Unidirectional control mechanism for a rotary drive linkage



Jan. 16, 1962 H. s. CARLSTON 3,017,173

UNIDIRECTIONAL CONTROL MECHANISM FOR A ROTARY DRIVE LINKAGE Filed Dec. 28, 1959 2 Sheets-Sheet l HA MIL TON 5. CA RLS TON INVENTO/P HUEBNER 8 WORREL A Tra /v5 rs MW!!! Jan. 16, 1962 H. s. CARLSTON 3,017,173

UNIDIRECTIONAL CONTROL MECHANISM FOR A ROTARY DRIVE LINKAGE I Filed Dec. 28, 1959 2 Sheets$heet 2 wy/M United States Patent 9 3,017,173 UNIDIRECTIONAL CONTRGL MECHANISM FOR A ROTARY DRIVE LINKAGE Hamilton S. Carlston, 556 Tower Ave, Fresno, Calif. Filed Dec. 28, 1959, Ser- No. 862,195 11 Claims. (Cl. 268119) The present invention relates to a unidirectional control mechanism for a rotary drive linkage and more particularly to a mechanism for controlling the movement of a crank-out type window and other closure members which are mounted on hinges for movement between open and closed positions.

Many modern buildings utilize a so called crank-out type of window which has a rectangular, steel casement mounted to swing horizontally about a vertical axis. A drive linkage is mounted on the window in a gear box and is provided for swinging the casement between open and closed positions. This linkage usually includes a worm wheel rotatably mounted in the gear box, a lever rigidly outwardly extended from the wheel and slidably connected to the casement, a crank journaled in the box and extended within the building adjacent to the window, and a worm gear connected to the crank and in mesh with the worm wheel. Thus, the crank is rotatable in opposite directions to rotate the worm wheel and thereby to swing the casement between its open and closed positions.

In order to provide a desired minimum amount of ventilation, these windows are often left ajar. It has been known in the past for burglars, and othertintruders, to reach through such a narrow opening, to grasp the crank, and to turn the crank so as to open the window. In this manner, the intruder provides a suifi-ciently wide opening to permit entrance to the house through thewindow.

In the prior United States Patent No. 2,610,848, a unidirectional control mechanism is disclosed for obviating the described problem. Essentially this patent describes a ratchet mechanism connected to the crank which, if operated with the window open, precludes opening of the casement beyond a predetermined position until the casement is first closed. The subject invention is a further development in this type of unidrectional control mechanism particularly adapted for use with crank-out type windows. 7

Accordingly, it is an object of the present invention to provide improvements in a unidirectional control mechanism for a drive linkage.

Another object is to provide a drive linkage including a driven member normally rotatable in opposite directions by a driving member, and a selectively operable mechanism for permitting only unidirectional rotation of the drive and driven members until the members have been rotated through a predetermined angle in said one direction.

Another object is to minimize unauthorized intrusion into a building through a partially open casement window.

Another object is to prevent unauthorized intruders from reaching through a partially open crank-out type casement window for opening the window farther by rotation of the crank.

Another object is to prevent a crank-out type casement window from being opened beyond a predetermined position until the window is first closed.

Another object is to provide a unidirectional control mechanism of the type described which is simple, economical, durable, and more effective for the purposes described than heretofore known.

Another object is to provide a control mechanism of the nature discussed above which is readily incorporated windows.

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These, together with other objects, will become more fully apparent upon reference to the following description and accompanying drawings.

In the drawings:

FIG. 1 is a fragmentary, horizontal cross section of a crank-out type casement window incorporating an embodiment of the control mechanism of the subject invention.

FIG. 2 is a somewhat enlarged, fragmentary, vertical section taken on a plane at a position represented by line 2-2 of FIG. 1 but showing the casement window in closed position.

FIG. 3 is a somewhat enlarged, fragmentary plan view, partially in section, of a control mechanism as used in the casement window illustrated in FIGS. 1 and 2 and therefore embodying the principles of the present invention.

FIG. 4 is a view similar to FIG. 3 but showing the gear box of the mechanism broken away to enable observation of the interior of the box and the parts of the mechanism therein.

FIG. 5 is a vertical section taken on a plane at a position represented by line 55 of FIG. 4 with the control mechanism in unlocked position.

FIG. 6 is a view similar to FIG. 5 but showing the mechanism in locking position.

FIG. 7 is a transverse vertical section taken on a plane at a position represented by line 77 of FIG. 6.

FIG. 8 is a somewhat enlarged, perspective, detail view of a pawl utilized in the mechanism of the subject in vention.

FIG. 9 is a view similar to FIG. 5 but showing another form of the mechanism of the subject invention in unlocked position.

FIG. 10 is a view similar to FIG. 9 but showing this form of the invention in locking position.

Referring more particularly to the drawings, a building wall is partially illustrated in FIGS. 1 and 2 and is identified by the numeral 10. The wall has a window 11 including a horizontal sill 12, a substantially rectangular frame 14 circumscribing a window opening, and a rectangular casement 16 mounting a glass window pane 17 therein. The casement is supported by hinges 18 for movement between a position engaging the frame and closing the window and angularly outwardly extended positions, one of which isv illustrated in FIG. 1, wherein the window is either fully opened or partially opened. This window construction is conventional and is not referred herein in any greater detail.

A crank-out mechanism for opening and closing the window 11 is generally indicated by the numeral 25. This mechanism includes a. gear box or housing 26 secured to a lower horizontal portion of the window frame 14 immediately above the window sill 12 by means of bolts or screws 27. The gear box has a curved back wall 30, horizontal top and bottom walls 31 and 32, and a lateral wall 33 continuous with the back wall. The top wall includes an inwardly upwardly extended collar 35 and provides a slot 36 adjacent to the collar.

With particular reference to FIGS. 5 and 6, a pair of vertically spaced bosses 40 are integrally extended from the top and bottom walls 31 and 32 of the gear box 26, and therewithin, in laterally spaced relation to the collar 35. A driven worm wheel 42 is rotatably mounted between the bosses by means of a vertical pin or shaft 43 extended through the bosses and connected to the gear box. An angulated lever 45 of conventional construction is integrally outwardly extended from the worm wheel and connected to the lower edge of the easement 16 for sliding movement therealong in a track, generally indicated by the numeral 47.

A' cylindrical bearing 55 is screw-threaded within the collar '35 and rotatably journals a hand crank 56 within the collar. The crank has an outer manipulating end portion 57 and an inner mounting end portion or shaft 58 adjacent to the worm wheel 42. A worm gear 59 is coaxially mounted on the inner end portion of the crank, or integrally formed thereon, and is in mesh with the worm wheel. Therefore, as is well-known in crankout windows of this type, rotation of the crank, which forms a drive member, effects rotation of the worm wheel 42 and thereby causes the casement to pivot on its hinges 18 between open and closed positions of the window 11.

The subject invention provides a ratchet wheel 65 concentrically rigidly mounted on the inner end portion 58 of the crank 56 inwardly of the bearing 55, as best seen in FIGS. 3, 5, and 6. A pawl 66 is pivotally mounted in the gear box 26 by means of a substantially horizontal pin 6-7 extended into the box through the back wall 38 and relatively adjacent to the lateral wall 33, as indicated in FIG. 4. The pawl has a bore 69 opening outwardly thereof in opposed relation to the lateral wall 33, a tooth 70 extended toward the ratchet wheel for engagement therewith, a rounded shoulder 71 on the opposite side of the pawl from said bore, and a substantially horizontal camming edge 72 concentric to the pin 43 but radially outwardly spaced from the worm wheel 4-2, as illustrated in FIG. 4.

An adjustment plug 78 is screw-threaded into a bore in the lateral wall 33 in coaxial alignment with the bore 69 in the pawl '66. A compression spring 79 is fitted in the bores of the pawl and the lateral wall and bears against the plug as well as the pawl. It is to be noted that the force applied by the compression spring to the pawl is below the pivot axis, as defined by the pin 67, for the pawl. Thus, the spring yieldably urges the pawl to rotate in a counterclockwise direction, as viewed in FIGS. and 6. This yieldably urges the tooth 70' of the pawl toward ratchet wheel engagement.

A trigger 85- is also mounted on a substantially horizontal pin 86 connected within the gear box 2 6 but above and laterally of the pin 67. The trigger is fitted in the slot 36 and has a manipulating handle 87 extended out of the box, a lower locking notch 89 defined by spaced upper and lower prongs 9t) and 91 and adapted to receive the shoulder 71 of the pawl 66 in relative predetermined pivoted positions of the pawl and the trigger, an inner stop 95 extended laterally from the pin 86 toward the lateral wall 33, and an outer stop 96 extended upwardly from the pin 86. The center-of mass of the trigger is located to the right of the pivot pin 86, as viewed in FIG. 5, because more of the weight of the trigger is in the handle than in the other portions of the trigger to the left of the pivot pin. Therefore, the trigger is gravitationally urged in a clockwise direction, as viewed in FIG. 5, into a position with the inner stop 95 in engagement with the top wall 31 of the gear box. This is hereinafter referred to as the cocked position of the trigger. In the cocked position of the trigger, the shoulder of the pawl is fitted in the locking notch 89' of the trigger. However, the trigger is manually movable in a counterclockwise direction from its cocked position into a released position, as illustrated in FIG. 6, with the outer stop 96 engaging the collar 35. In moving toward released position, the upper prong slides downwardly and laterally over the shoulder. That is, the upper prong is moved out of the path of movement of the shoulder. This al- 'lows the spring 79 to urge the pawl in a clockwise direction, as viewed in FIGS. 5 or 6, into a locking position with its tooth 70 in engagement with the ratchet wheel 65.

With the pawl 66 in its locking position, as described above, the tooth 70 permits rotation of the ratchet wheel 65 in a counterclockwise direction, as viewed in FIG. 6, but precludes rotation of the ratchet wheel in a clockwise direction. This is so because when the teeth of the ratchet wheel, in turning counterclockwise, bear against the tooth of the pawl, the ratchet wheel urges the pawl in a clockwise direction. This movement is permitted since the shoulder 71 slides downwardly against the upper prong 90 and because the pawl can pivot in this direction. Thus, each tooth of the ratchet wheel slides over the tooth of the pawl. However, when an attempt is made to rotate the ratchet wheel in a clockwise direction, the length of the tooth 76 in relation to the spacing of the pin 67 from the axis of rotation of the ratchet wheel 65 is such that such rotation is precluded.

It is also to be observed that when the pawl 66- is in its locking position, as illustrated in FIG. 6, the camming edge 72 of the pawl is slightly above the path of travel of the camming finger 50. Therefore, if the worm. wheel 4-2 is rotated in a clockwise direction, as viewed in FIG. 4, a sufficient amount, the camming finger moves into engagement with the camming edge. The finger thereby bears down on the pawl and pivots the same in a clockwise direction against the urgence of the spring 79. As the camming finger rides upwardly on the camming edge, the pawl continues to rotate until the shoulder 71 slides under the upper prong 90 and into the notch 89. Because the trigger is gravitationally urged to rotate in a clockwise direction, as soon as the shoulder is moved down under the upper prong, the trigger falls into its cocked position and thereby holds the pawl in its unlocked position, as viewed in FIG. 5.

Operation The operation of the described embodiment of the subject invention is believed to be readily apparent and is briefly summarized at this point.

The subject invention may be used when it is desired to leave the window 11 partially open for ventilation purposes, for example, but at the same time to avoid the unauthorized intrusion of burglars. For such use the casement 16 is pivoted outwardly by means of the crank 56 into a position, such as that illustrated in FIG. 1, providing the desired extent of ventilation. So positioned, the window is partially open but there is not sufficient space between the outer edge of the casement and the frame to permit unauthorized entrance therethrough. In order to place the unidirectional control mechanism of the subject invention into operation, the trigger 85 is manually lifted, that is pivoted in a counterclockwise direction as viewed in FIG. 5, into its released position. The spring 79 thereupon urges the pawl 66 into its locking position. Thereafter, the crank can move the casement 16 only toward closed position. Reference to FIGS. 4 and 6 clearly reveals this operation.

The window is opened or closed by rotating the crank in a counterclockwise or a clockwise direction, respectively. The ratchet wheel 65 of course turns in the same direction as the crank. Therefore, since the pawl in locking position precludes clockwise rotation of the ratchet wheel, it therefore precludes outward, opening movement of the casement.

In order to release or unlock the pawl 66, it is necessary to close the easement 16 completely, Therefore, the crank 56 is turned in a counterclockwise direction to rotate the worm wheel 42 in a clockwise direction, as viewed in FIG. 4. As the casement moves into close engagement with the frame 14, the camming finger 50 engages the camming edge 72 so that when the easement is completely closed, the camming finger has moved the pawl 66 into its unlocked position. As explained above, the trigger 85 gravitationally moves into cocked position to hold the pawl in unlocked position. Therefore, with the tooth 70 disengaged from the ratchet wheel 65, the crank 56 is free to turn in a clockwise direction to open the window 11.

The effect of this mechanism is believed obvious.

-While an intruder may be able to reach through the horizontal pin 119.

Second form The second form of the subject invention is illustrated in FIGS. 9 and 10. These figures show a gear box or housing 109 including a top wall 101 having a collar 102, a lateral wall 103, and a bottom wall 104. The basic construction and shape of the gear box is like that of the first form of the invention.

A pair of bosses 1118 is provided within the gear box in extension from the top and bottom walls 101 and 104, and a worm wheel 109 is journaled between the bosses. As before, a camming finger 1151 is rigidly, radially, outwardly extended from the worm wheel. Although not shown, the worm wheel is connected to a casement of a window by means of a lever, all as illustrated and described in connection with the first form of the invention.

A ratchet wheel 115 is secured to a crank 116, and a pawl 118 is pivoted in the gear box 100 by mean of a The pawl includes a tooth 121 adapted for engagement with the ratchet wheel, a camming edge 122, and a guide projection 124 on the opposite side of the pivot pin from the camming edge. The guide projection is also offset below the pin.

A plug 130 is screw-threaded in the lateral wall 1% of the gear box and has a socket 131 directed into the box. An over-center compression spring 133 has one end fitted over the guide projection 124 and an opposite end received in the socket of the plug. The spring urges the pawl into either a locking position, as viewed in FIG. 10, when the axis of the spring is directed downwardly below the pivot pin 119, or an unlocked position, as viewed in FIG. 9, when the axis of the spring is directed upwardly above the pivot pin.

A trigger 140 includes a straight shank 141 s lidably mounted in the lateral wall 103 of the gear box 100' along an axis extended downwardly and inwardly of the box slightly below the pivot pin. The shank has an inner enlarged head 142 and an opposite threaded end 143 on which is screw-threaded a cap 145. A'coiled compression spring 146 circumscribes the shank outside of the box and bears against the cap adjacent to the threaded end and also .against the lateral wall of the box thereby to urge the shank of the trigger outwardly of the box and to bring the head into engagement with the lateral wall of the box. The trigger has a released position, as illustrated in FIGS. 9 and 10, and a locking position inwardly slidably extended into the box wherein the head of the trigger engages the projection 124 on the pawl and pivots the pawl in a counterclockwise direction into its clocking position.

In operation, when the pawl 118 is in its unlocked position, as viewed in FIG, 9, the unidirectional control mechanism is disabled and the crank-out window is opened or closed in the usual manner. When it is desired to effect unidirectional control of the rotation of the crank 116, the trigger 140 is pressed inwardly to move the pawl 118 into its locked position, as viewed in FIG. 10. Thereafter, the crank is prevented from rotating in a clockwise direction to open the window, not shown, but is permitted to rotate only in a counterclockwise direction to close the window. After the worm wheel 109 is moved through a sufiicient angle in a clockwise direction, the camming finger 110 engages the camming edge 122 of the pawl and pivots the pawl in a clockwise direction to throw the spring over-center and into its upwardly directed position whereby the pawl is held in its unlocked position, as seen in FIG. 9. As with the first form of the invention,

6 the engagement of the oamming finger with the camming edge of the pawl occurs when the window, not shown, is closed.

From the foregoing, it is evident that a unidirectional control mechanism has been provided for a drive linkage and particularly applicable to crank-out casement type windows. The mechanism is controllable so that it can be brought into use as desired but, when disabled, does not interfere with the normal operation of the linkage system. When utilized in connection with crank-out windows, of the type described, the subject invention prevent unauthorized intrusion into buildings, or the like, through partially open windows. The mechanism is readily adaptable to conventional crank-out apparatus and is simple, economical, durable, and highly dependable for performing its intended functions.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a drive linkage, a support, a driven member journaled in the support, and a drive member journaled in the support and having driving connection to the driven member for rotating the driven member selectively in opposite directions in response to rotation of the drive member in opposite directions; a selectively operable mechanism for allowing only unidirectional rotation of the members comprising a ratchet wheel connected to the drive member for rotation therewith; a pawl pivotally mounted in the support for movement between locked and unlocked positions respectively in engagement with and disengaged from the ratchet wheel; control means mounted in the support engaging the pawl for holding the pawl in unlocked position and being operable for moving the pawl into locked position; pawl unlocking means connected to the driven member and engageable with the pawl in a predetermined angular position of rotation of the drive member for moving the pawl from locked into unlocked position, the control means includ- .ing an over-center spring positioned between the support and the pawl alternately yieldably urging the pawl into engagement with the ratchet wheel and out of such engagement, and a trigger mounted in the support for movement to a position engaging the pawl for urging the pawl from its unlocked position a distance sufficient for the over-center spring to urge the pawl into locked position and for movement to a position retracted from the pawl.

2. In a support providing a window opening, a casement mounted on the support for movement between a closed position in the opening and an open position, a driven gear rotatably mounted in the support, a crank rotatably journaled in the support having :driving connection to the driven gear for rotating the driven gear incident to rotation of the crank, and a lever interconnecting the driven gear and the casement for moving the casement between open and closed positions upon rotation of the driven gear; a mechanism for precluding movement of the casement beyond a predetermined open position until the easement is first moved into closed position comprising a first ratchet member connected to the crank; a second ratchet member mounted in the support for movement between a position engaging the first ratchet member and a position disengaged from said first member, said first and second members permitting rotation of the crank only in the direction required for closing the easement when said members are engaged; control means mounted in the support engaging the second ratchet member for releasably holding it out of engagement from said first member but being operable to urge the second member into engagement with the first member; ratchet unlocking means borne by the driven gear and engaging the second ratchet member in the closed position of the easement if the second member is in engagement with the first member to disengage the first and second mem bers; and a pivot pin mounted in the support in laterally spaced, acute angular relation to the crank, the second member being pivotally journaled on the pin, said control means including a projection outwardly extended from the second member on the opposite side of the pivot pin from the first ratchet member, a compression spring having a longitudinal axis and being fitted over the projection and bearing against the support for yieldably urging the second member into said disengaged position when the axis of the spring is extended on the side of the pivot pin adjacent to said first ratchet member and into said engaged position when the axis of the spring is extended on the opposite side of the pivot pin from said first member, and an elongated trigger longitudinally slidably mounted in the support for movement into engagement with the projection when the second member is in disengaged position for pivoting said second member on its pin and moving the axis of the spring to said opposite side of the pin whereby the spring moves said second member into engaged posittion.

3. In a motion transmitting apparatus including a support, a driven shaft rotatably journaled in the support, a worm wheecl rigidly connected to the driven shaft, a drive shaft rotatably journaled in the support, and a worm coaxially mounted on the drive shaft and in mesh with the worm wheel for rotating the worm wheel in opposite directions about its axis in response to rotation of the drive shaft in opposite directions about its respective axis; a mechanism for optionally precluding rotation of the drive shaft in one direction until the drive shaft has been rotated through a predetermined angle in the opposite direction comprising a ratchet wheel concentrically rigidly connected to the drive shaft; a pawl; means pivotally mounting the pawl in the support for movement between locking and unlocked positions respectively in engagement with and disengaged from the ratchet wheel; control means mounted in the support engaging the pawl for holding the pawl in unlocked position and being operable for moving the pawl into locked position; and a finger rigidly connected to the worm wheel and engageable with the pawl in a predetermined angular position of rotation of the drive shaft for moving the pawl into unlocked position if the pawl is in locked postion.

4. In a motion transmitting mechanism including a support, a driven shaft rotatably journaled in the support, a worm wheel rigidly connected to the driven shaft, a drive shaft rotatably journaled in the support, and a worm gear coaxially mounted on the drive shaft and in mesh with the worm wheel for rotating the driven shaft in opposite directions about its axis in response to rotation of the drive shaft in opposite directions about its respective axis; an apparatus for optionally precluding rotation of the drive shaft in one direction until the drive shaft has been rotated through a predetermined angle in the opposite direction comprising a ratchet wheel concentrically rigidly connected to the drive shaft; a pawl; means pivotally mounting the pawl in the support for movement between locking and unlocked positions respectively in engagement with and disengaged from the ratchet wheel; resilient means mounted in the support, engaging the pawl, and yieldably urging the pawl toward said locking position; a trigger mounted in the support for movement between a cocked position engaging the pawl for holding the pawl in unlocked position and a re leased position allowing said resilient means to urge the pawl into locking position, said trigger being urged toward cocked positions; and a finger rigidly connected to the worm wheel and engageable with the pawl in a predetermined angular position of rotation of the drive shaft and when the pawl is in locking position for moving the pawl into unlocked position and permitting movement of the trigger into cocked position, whereby with the finger out of pawl engagement, if the trigger is moved into released position, the drive shaft can only be rotated in said opposite direction until the drive shaft is moved into said predetermined position.

5. In a motion transmitting apparatus including a support, a driven shaft rotatably journaled in the support, a worm wheel rigidly connected to the driven shaft, a drive shaft rotatably journaled in the support, and a worm gear coaxially mounted on the drive shaft and in mesh with the worm wheel for rotating the driven shaft in opposite directions about its axis in response to rotation of the drive shaft in opposite directions about its respective axis; an apparatus for optionally precluding rotation of the drive shaft in one direction until the drive shaft has been rotated through a predetermined angle in the opposite direction comprising a ratchet wheel eoncentrically rigidly connected to the drive shaft; a pawl including a tooth, a shoulder, and a camming edge; means pivotally mounting the pawl in the support for movement between locking and unlocked positions with the tooth respectively in engagement with and disengaged from the ratchet wheel; resilient means mounted in the support, engaging the pawl, and yieldabl; urging the pawl toward said locking position; a trigger mounted in the support for movement between'a cocked position engaging the shoulder of the pawl for holding the pawl in unlocked position and a released position allowing said resilient means to urge the pawl into locking position, said trigger being urged toward cocked position; and a finger rigidly connected to the worm wheel and engageable with said camming edge of the pawl in a predetermined angular position of rotation of the drive shaft and when the pawl is in locking position for moving the pawl into unlocked position and permitting movement of the trigger into cocked position, whereby with the finger out of pawl engagement, if the trigger is moved into released position, the drive shaft can only be rotated in said opposite direction until the drive shaft is moved into said predetermined position.

6. The mechanism of claim 3 wherein the control means includes a spring mounted in the support in engagement with the pawl for yieldably urging the pawl into engagement with the ratchet wheel, and a trigger pivotally mounted in the support for movement between a cocked position in the path of the pawl to hold the pawl in unlocked position and a released position out of the path of the pawl to permit the spring to urge the pawl into locking position.

7. The mechanism of claim 3 including a first pivot pin mounted in the Support in laterally spaced relation to the first ratchet member, the second ratchet member being journaled on the pin for movement between said engaged and disengaged positions, the second member having a shoulder laterally extended on one side of the pivot pin, the control means including a compression spring engaging the support and said second member on the opposite side of the pivot pin from the first ratchet member and from the shoulder for applying a turning moment to the second member for urging it into said engaged position, said control means further including a second pivot pin mounted in the support in spaced parallel relation to the first pivot pin and on the same side thereof as said shoulder, and a trigger journaled on the second pivot pin having a notch releasably receiving the shoulder to hold the second member in disengaged position, the trigger being pivotal on the second pivot pin to enable release of the shoulder from the notch and to permit the spring to urge the second member into engaged position.

8. In a motion transmitting apparatus including a support, a worm wheel, means rotatably journaling the worm wheel in the support, a drive shaft rotatably journaled in the support, and a worm coaxially mounted on the drive shaft and in mesh with the worm wheel for rotating the worm wheel in opposite directions about its axis in response to rotation of the drive shaft in opposite directions about its respective axis; a mechanism for optionally precluding rotation of the drive shaft in one direction until the drive shaft has first been rotated through a predetermined angle in the opposite direction comprising a ratchet wheel concentrically rigidly connected to the drive shaft; a pawl; means pivotally mounting the pawl in the support for movement between locked and unlocked positions respectively in engagement with and disengaged from the ratchet member; control means mounted in the support engaging the pawl for holding the pawl in unlocked position and being operable for moving the pawl into locked position; and a finger rigidly connected to the worm wheel and engageable with the pawl in a predetermined angular position of rotation of the drive shaft for moving the pawl into unlocked position from locked position.

9. In a motion transmitting apparatus including a support, a driven shaft rotatably journaled in the support, a worm Wheel rigidly connected to the driven shaft, a drive shaft rotatably journaled in the support, and a worm coaxially mounted on the drive shaft and in mesh with the worm wheel for rotating the worm wheel in opposite directions about its axis in response to rotation of the drive shaft in opposite directions about its respective axis; a mechanism for optionally precluding rotation of the drive shaft in one direction until the drive shaft has first been rotated through a predetermined angle in the opposite direction comprising a ratchet wheel concentrically rigidly connected to the drive shaft; a pawl; means pivotally mounting the pawl in the support for movement between predetermined locked and unlocked positions respectively in engagement with and disengaged from the ratchet wheel, control means mounted in the support engaging the pawl for holding the pawl in unlocked position and being operable for moving the pawl into locked position, said control means including an over-center spring position between the support and the pawl alternately yieldably urging the pawl into engagement with the ratchet wheel and out of such engagement, and a trigger mounted in the support for movement to a position engaging the pawl for urging the pawl from its unlocked position a distance sufiicient for the over-center spring to urge the pawl into locked position and for movement to a position retracted from the pawl, and a finger rigidly connected to the worm wheel and engageable with the pawl in a predetermined angular position of rotation of the drive shaft for moving the pawl into unlocked position if the pawl is in locked position.

10. In combination with a support and a rotary drive linkage rotatably mounted in the support for rotation in opposite directions about a predetermined axis of rotation; a mechanism for optionally precluding rotation of the linkage in one direction until the linkage has first been rotated through a predetermined angle in the opposite direction comprising a ratchet member borne by the linkage for rotation therewith and including a plurality of teeth circumferentially spaced about said axis; articulated means including a pawl portion and being mounted in the support for movement between a locked position with the pawl portion in engagement with teeth on the ratchet member and an unlocked position with the pawl portion disengaged from said teeth; a trigger mounted in the support for movement between a locking position engaging the articulated means and urging the same from unlocked to locked position, and a released position retracted from said locking position; and means borne by the linkage and engageable with said pawl portion in the locked position of the articulated means and in a predetermined angular position of rotation of the linkage for moving the articulated means into unlocked position.

11. In combination with a support and a rotary drive linkage rotatably mounted in the support for rotation in opposite directions about a predetermined axis of rotation; a mechanism for optionally precluding rotation of the linkage in one direction until the linkage has first been rotated through a predetermined angle in the opposite direction comprising a ratchet member borne by the linkage for rotation therewith and including a plurality of teeth circumferentially spaced about said axis; a pivot pin mounted in the support in laterally spaced relation to the ratchet member; a pawl mounted on the pin for rotation thereon between locked and unlocked positions respectively in engagement with and disengaged from teeth on the ratchet member; a compression spring having a longitudinal axis and being positioned between the support and the pawl with its longitudinal axis extended transversely of the pivot pin for yieldably urging the pawl into said unlocked position with the axis of the spring extended on the side of the pivot pin adjacent to the ratchet member and into said locking position with the axis of the spring extended on the opposite side of the pivot pin from said ratchet member; a trigger mounted in the support for movement between a locking position engaging the pawl in the unlocked position thereof for overcoming the urgence of the spring and moving the pawl into its locking position, and a released position retracted from said locking position; and a finger rigidly connected to the linkage and engageable with the pawl in the locked position thereof and in a predetermined angular position of rotation of the linkage for moving the pawl into unlocked position.

References Cited in the file of this patent UNITED STATES PATENTS 1,274,471 Todd Aug. 6, 1918 1,414,000 Todd Apr. 25, 1922 1,827,746 Hansen Oct. 20, 1931 1,967,481 Schaffert July 24, 1934 2,610,848 Carlston et al. Sept. 16, 1952 

